Transfer cathode thyratron



A g. 18, 1959 R. G, FOWLER 2,900,550

TRANSFER CATHODE THYRATRON Filed Jail. 24, 1957 ramss P0154 INVENTOR.

R/CHARD FOWLER I flrroem United rates Patent TRANSFER CATHODE THYRATRON Richard G. Fowler, Norman, 0kla., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application January 24, 1957, Serial No. 636,221!

8 Claims. (Cl. 313-189) This invention relates to thyratrons and more particularly to a transfer cathode thyratron. Prior art conventional thermionic thyratrons suifer from the defect that high cathode currents cannot be obtained without sacrificing the rapid rise time of the conduction characteristic of the ordinary thyratron.

An object of the present invention is to provide a thyratron in which this limitation on cathode current is removed.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description and from the single figure which represents a more or less schematic cross-section of part of a preferred embodiment of the invention as connected in a typical circuit.

In the figure the envelope of a more or less conventional hydrogen thyratron is indicated at 2. The structure is basically nearly identical with that of the thyratrons described on pages 338, 339, and 340 of the book entitled Pulse Generators constituting volume 5 of the MIT Radiation Laboratory Series published by McGraw- Hill Book Company, 1948. The tube includes an anode 4 shielded by a grid structure 6 and one or more baffles 8. A thermionic cathode 10 surrounded by a heat shield 12 is capable of delivering a number of amperes of current. An accelerating anode 14 is located adjacent the thermionic cathode and a cold cathode 16 is interposed between the thermionic cathode and the anode. While the particular embodiment illustrated in the figure shows 14 and 16 as separate elements, in some embodiments they can be combined into one if desired, which would be represented by 16. An opening 22 is provided in the cold cathode 16 to facilitate the passage of electrons from the hot cathode toward the anode. The cold cathode 16 is made of any suitable refractory metallic material such as nickel, platinum, tungsten or the like. In some embodiments it may be advantageous for it to have low Work function emissivity.

To use the invention thermionic cathode 10 and accelerating anode 14 are connected in a circuit through moderate impedances Z and Z respectively, while the cold cathode 16 is connected through a low impedance Z, to the same energy source, E, which activates the anode 4. The circuit includes a load Z Means are provided to vary the potential on the grid 6 and also on the accelerating anode 14. The means may be, for example, a source of voltage arranged to supply a trigger pulse or the like across Z and across Z Le. between terminal 18 and ground and between terminal 20 and ground.

In operation, initially 6, 14, 16, and 10, are at or near the same potential. A rise in potential, relative to ground, in 6 and 14 (caused by a trigger pulse) releases thermionic electrons from 10 to initiate a discharge throughout the tube. The hole 22 in the cathode 16 facilitates this operation by furnishing a passage for the electrons. The impedances Z and Z in series with thermionic cathode 10 and accelerating anode 14, respectively, cause the potentials relative to ground of elements 10 and 14 to rise above that of cold cathode 16 thus reducing the potential difierence between each of elements 10 and 14 "ice and the anode 4, on the one hand, below the potential difference existing between the cold cathode 16 and anode 4, on the other hand, with consequent preferential transfer of the discharge to 16 as cathode. The current capacity of the device is considered to be far in excess of that of an ordinary prior art hydrogen thyratron.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a thyratron having an anode, a hot cathode, and a grid, the improvement which comprises an accelerating anode adjacent the hot cathode and interposed between the hot cathode and the anode; and a cold cathode, said cold cathode being disposed on the extension of the straight line defined by the path of electrons flowing through said grid to said anode and being spaced from said grid a distance, measured in the direction of said straight line, in excess of the mean free path of electrons under the pressure present in said thyratron.

2. The thyratron of claim 1 wherein said cold cathode is interposed between said accelerating anode and said first mentioned anode.

3. T he thyratron of claim 2 wherein said cold cathode is pierced with an opening extending in the path of electrons emanating from said hot cathode and travelling toward said anode whereby electrons from said hot cathode can reach the interspaee between said cold cathode and said anode.

4. The thyratron of claim 3 wherein said cold cathode is in the form of a pierced plate spanning the region adjacent said accelerating anode occupied by electrons emitted from said hot cathode travelling toward said anode.

5. In a hydrogen thyratron having an anode, a hot cathode, and a grid, the improvement comprising a cold cathode, said cold cathode being disposed on the extension of the straight line defined by the path of electrons flowing through said grid to said anode and being spaced from said grid a distance, measured in the direction of said straight line, in excess of the mean free path of electrons under the pressure present in said thyratron.

6. The device of claim 5 wherein the cold cathode is interposed between the hot cathode and the anode.

7. The device of claim 5 wherein the cold cathode is located closer to the hot cathode than to the anode.

8. -An apparatus comprising a thyratron including a hot cathode, a cold cathode, an anode, and a grid; means for applying a potential difference between said hot cathode and one of said other tube elements to initiate thermionic operation of said thyratron; and means for pro ducing a greater potential diiference between said anode and said cold cathode on the one hand than between said anode and said hot cathode on the other hand to effect a preferential transfer of the discharge in said thyratron from said hot cathode to said cold cathode, said cold cathode being disposed on the extension of the straight line defined by the path of electrons flowing through said grid to said anode and being spaced from said grid a distance, measured in the direction of said straight line, in excess of the mean free path of electrons under the pressure present in said thyratron:

References Cited in the file of this patent UNITED STATES PATENTS 1,962,158 Smith June 12, 1934 1,962,159 Le Van June 12, 1934 2,058,738 Laurent Oct. 27, 1936 2,228,276 Le Van Jan. 14, 1941 

